Production of SNG from Biomass Using a Commercial-Scale Fluidized Bed Gasifier Integrated with Water Electrolysis

Biomass gasification, as a thermochemical process, has attracted growing interest due to the increasing popularity of biofuel production based on syngas or pure hydrogen. Moreover, when integrated with CO2 capture, this method of producing gaseous fuels can achieve negative CO2 emissions, making it competitive with other production systems based on either fossil or renewable sources. This paper presents the results of a process and economic analysis of synthetic natural gas (SNG) production systems integrated with a commercial fluidized-bed gasification reactor based on Synthesis Energy Systems (SES) technology. The study examines the potential integration of the system with a water electrolyzer at two levels of coupling: one providing oxygen for the gasification process, and the other eliminating the need for CO2 separation before the SNG synthesis stage. Using a single gasification unit with a raw biomass feed rate of 60 t/h, the system produces 188 t/d of SNG. Integration with a water electrolyzer increases SNG production to 259 and 621 t/d. For cases without electrolyzer integration and under the assumption of zero emissions from biomass processing, the application of CO2 separation enables the achievement of negative CO2 emissions. This creates an opportunity for additional revenue from the sale of CO2 emission allowances, which can significantly reduce SNG production costs. In this analysis, the break-even CO2 price, above which the SNG production cost becomes negative, is USD 251/t CO2. In systems integrated with water electrolysis, the cost and carbon footprint of the electricity consumed in the electrochemical water-splitting process have a decisive impact on both the overall SNG production cost and its carbon intensity.